N = int(input())
C = input()
R = C.count("R")
ans = 0

for r in range(R):
  if C[r]=="W":
    ans+=1

print(ans) N = int(input()) N int(input()) int input() input C = input() C input() input R = C.count("R") R C.count("R") C.count C count "R" ans = 0 ans 0 for r in range(R):
  if C[r]=="W":
    ans+=1 r range(R) range R if C[r]=="W":
    ans+=1 C[r]=="W" C[r] C r "W" ans+=1 ans 1 print(ans) print ans N = int(input()) int(input()) N ans = 0 0 ans R = C.count("R") C.count("R") R C = input() input() C ans+=1 1 ans
N = int(input())
C = input()
R = C.count("R")
ans = 0

for r in range(R):
  if C[r]=="W":
    ans+=1

print(ans)